Signaling RX/TX beamforming linkage for MIMO systems

Abstract

The specification and drawings present methods and apparatuses for feedback signaling for beamforming purposes in a multiple input-multiple output (MIMO) radio environment. According to an embodiment of the invention, a mobile device is configured to measure an integer number P of different beam groups, each group representing one or more transmit beams and each group corresponding to one or more antenna ports at the mobile device. The mobile device is triggered according to the configuration to provide feedback. The radio access node transmits reference signals on each of the transmit beams across all of the groups for measurement by the mobile device and receives the triggered feedback including, for each of the different beam groups, at least one best match between a transmit beam of the respective group and a corresponding antenna port and an indication of measurement results for the best match.

What is claimed is: 
     
       1. A radio access node comprising:
 at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the radio access node at least to: 
 configure a mobile device to measure an integer number P of different beam groups, each group representing one or more transmit beams and each group corresponding to one or more antenna ports at the mobile device, wherein the one or more transmit beams per each beam group out of the different beam groups are grouped by using a same receive beamforming in the mobile device; 
 trigger the mobile device to provide feedback according to the configuration; 
 transmit reference signals on each of the transmit beams across all of the groups for measurement by the mobile device; and 
 receive from the mobile device the triggered feedback comprising, for each of the different beam groups, at least one best match between a transmit beam of the respective group and a corresponding antenna port and an indication of measurement results for the best match. 
 
     
     
       2. The radio access node according to  claim 1 , wherein the reference signals are beam reference signals. 
     
     
       3. The radio access node according to  claim 1 , wherein the triggering is periodic and the triggered feedback is received in a subframe that maps from a subframe in which the reference signals were transmitted. 
     
     
       4. The radio access node according to  claim 1 , wherein the triggering is aperiodic and the triggered feedback is received in a physical uplink shared channel multiplexed with data. 
     
     
       5. The radio access node according to  claim 1 , wherein the triggering is aperiodic and the triggered feedback is received in a media access control message on a physical uplink shared channel with data. 
     
     
       6. The radio access node according to  claim 1 , the at least one memory and the computer program code further configured to, with the at least one processor, cause the radio access node at least to:
 configure the mobile device with an integer value for N that defines how many best-matches are to be reported for each of the P different beam groups in the triggered feedback, wherein the value of N for one or more of the P different beam groups is less than all of the beams in the individual ones of the one or more of the P different beam groups. 
 
     
     
       7. The radio access node according to  claim 1 , wherein each of the P different beam groups is associated with a group index, and wherein configuring the mobile device to measure the integer number P of different beam groups comprises signaling to the mobile device the respectively associated group indices of the P different beam groups. 
     
     
       8. A mobile device comprising:
 at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the mobile device at least to: 
 receive from a radio network a configuration to measure an integer number P of different beam groups, each group representing one or more transmit beams and each group corresponding to one or more antenna ports at the mobile device, wherein the one or more transmit beams per each beam group out of the different beam groups are grouped by using a same receive beamforming in the mobile device; 
 receive from the network a trigger to provide feedback according to the configuration; 
 measure reference signals on each of the transmit beams across all of the groups on the respectively corresponding one or more antenna ports; 
 determine, based on the measured reference signals, for each of the different beam groups at least one best match between a transmit beam of the respective group and a corresponding antenna port; and 
 transmit to the network the triggered feedback comprising the at least one best match for each of the different beam groups and an indication of the measuring that resulted in the best match. 
 
     
     
       9. The mobile device according to  claim 8 , wherein the reference signals are beam reference signals. 
     
     
       10. The mobile device according to  claim 8 , wherein the trigger is to provide periodic feedback and the triggered feedback is transmitted to the network in a subframe that maps from a subframe in which the reference signals that were measured were received. 
     
     
       11. The mobile device according to  claim 8 , wherein the trigger is to provide aperiodic feedback and the triggered feedback is transmitted to the network in a physical uplink shared channel multiplexed with data. 
     
     
       12. The mobile device according to  claim 8 , wherein the trigger is to provide aperiodic feedback and the triggered feedback is transmitted to the network in a media access control message on a physical uplink shared channel with data. 
     
     
       13. The mobile device according to  claim 8 , the at least one memory and the computer program code further configured to, with the at least one processor, cause the mobile device at least to:
 receive from the radio network a configuration for an integer value for N that defines how many best-matches are to be reported in the triggered feedback for each of the P different beam groups in the triggered feedback. 
 
     
     
       14. The mobile device according to  claim 8 , wherein each of the P different beam groups is associated with a group index, and the configuration to measure the integer number P of different beam groups identifies the P different beam groups via their respectively associated group indices. 
     
     
       15. The mobile device according to  claim 8 , wherein the at least one processor and the at least one memory including the computer program code, is further configured to operate with a 5G mmWave radio access technology. 
     
     
       16. A method comprising:
 receiving at a mobile device from a radio network a configuration to measure an integer number P of different beam groups, each group representing one or more transmit beams and each group corresponding to one or more antenna ports at the mobile device, wherein the one or more transmit beams per each beam group out of the different beam groups are grouped by using a same receive beamforming in the mobile device; 
 receiving at the mobile device from the network a trigger to provide feedback according to the configuration; 
 measuring at the mobile device reference signals on each of the transmit beams across all of the groups on the respectively corresponding one or more antenna ports; 
 from the measuring, determining at the mobile device for each of the different beam groups at least one best match between a transmit beam of the respective group and a corresponding antenna port; and 
 transmitting by the mobile device to the network the triggered feedback comprising the at least one best match for each of the different beam groups and an indication of the measuring that resulted in the best match. 
 
     
     
       17. The method according to  claim 16 , wherein the reference signals are beam reference signals. 
     
     
       18. The method according to  claim 16 , wherein at least one of:
 the trigger is to provide periodic feedback and the triggered feedback is transmitted to the network in a subframe that maps from a subframe in which the reference signals that were measured were received; 
 the trigger is to provide aperiodic feedback and the triggered feedback is transmitted to the network in a physical uplink shared channel multiplexed with data; or 
 the trigger is to provide aperiodic feedback and the triggered feedback is transmitted to the network in a media access control message on a physical uplink shared channel with data. 
 
     
     
       19. The method according to  claim 16 , further comprising:
 receiving from the radio network a configuration for an integer value for N that defines how many best-matches are to be reported in the triggered feedback for each of the P different beam groups in the triggered feedback. 
 
     
     
       20. The method according to  claim 16 , wherein each of the P different beam groups is associated with a group index, and the configuration to measure the integer number P of different beam groups identifies the P different beam groups via their respectively associated group indices.